Over 1,000 feet beneath the city of Detroit is a 1,500 acre sprawl of tunnels created by salt miners at the turn of the twentieth century. Over at Environmental Graffiti, there's a fascinating story about the rise and fall of Detroit as the great city of salt production. Discovered in the late nineteenth century, Detroit's salt deposits would prove lucrative — but only to the company with the engineering capabilities to actually drill down far enough to reach it.

As Environmental Graffiti's Simone Preuss explains:

The Detroit Salt and Manufacturing Company operated the mine until 1983 but then falling salt prices forced the mine to stop production. In its heyday in the 1920s, 1940s and ‘50s, the mine was open to the public with guided tours – a popular educational trip for school classes. Today, the entrance to the mine at 12841 Sanders Street is only for delivery trucks and public tours have not been conducted since the 1980s.

One of the many problems with working in such a deep mine was that equipment had to be lowered down the narrow shaft in pieces, then assembled at the bottom. Even donkeys were lowered down to work, and never brought back up.

Out of commission for many years, the mine was bought in the late 1990s and is now used mostly to produce rock salt. Here's hoping the new owners, Detroit Salt, will open it for tours again.